1. Field of the Invention
The present invention relates to the art of solar collection devices and pertains more particularly to a high efficiency, non-tracking solar collector device of the type in which liquid is circulated in heat exchange relation across the receptor surface against which solar energy is concentrated by an appropriate non-tracking reflector, lens or other concentrating device (the term "reflector" as hereinafter used to be interpreted to encompass any concentrator device).
2. Prior Art
With the current shortage of fuels, there has been progressively increasing interest in the utilization of solar energy, which interest, in no small measure, has been increased by the progressive rise in prices of conventional fuels, including oil, natural gas, wood, coal and the like.
Devices which capture the sun's rays at their ordinary incident intensity are limited to a certain maximum temperature range, and so for purposes which require higher temperatures it is common to concentrate the sun's rays with a curved reflector, lens, or similar device.
Numerous methods have been suggested for efficiently employing the concentrated rays of the sun as a source of heat. Obviously, it is desirable for a given area of reflector or concentrator surface that the maximum possible energy be extracted.
In accordance with a known type of solar collector, known as a tracking collector, a heat carrier liquid is circulated through a passage and the collected concentrated sun's rays are impinged against an external surface of the passage. The reflector or other concentrating device is provided with means for compensating for the varying angle of the sun whereby, notwithstanding variations in the sun's inclination, the collected rays are focused more or less precisely on the heat transfer surface of the passageway.
Numerous types of tracking mechanisms are employed for optimizing the azimuth angle of the concentrator or collector surface, including clock mechanisms, photo-electric guide systems and the like which orient the position of the concentrator relative to the collector. Such systems, while effective, are extremely expensive and are failure-prone, especially where conditions such as snow, high winds and ice are encountered, and require maintenance throughout the operating life of the installation.
In order to avoid the expense and difficulties inhering in tracking type solar collector devices, resort has been made to solar collectors operating on a non-tracking basis. Such devices incorporate a fixed (seasonally adjusted) reflector, normally elongate and oriented in an east-west direction, the reflector being curved so as to concentrate most of the incident rays along a linear path, the location of which varies in accordance with the inclination of the sun. A receptor member is disposed to receive the concentrated band of energy emanating from the reflector.
In certain such systems plural targets are present and means are provided for maximizing flow through that portion or those portions of the target or paths which are hottest.
The means heretofore employed for maximizing fluid flow through the path area in registry with concentrated energy have included heat sensors and solenoids (U.S. Pat. Nos. 3,915,148 Fletcher; 3,994,279 Barak; 4,121,566 Radenkovic; 4,153,955 Hinterberger); thermally activated valves (U.S. Pat. No. 4,103,673 Woodworth); change of state responsive energy extraction mechanisms (U.S. Pat. No. 4,052,976 Hinterberger) and variations and combinations of the above.